CN1248289C - Inductive coupling type plasma device - Google Patents

Abstract

An inductively coupled plasma device is provided. The inductively coupled plasma device includes a processing chamber, a top plasma source chamber, a reactor, an inductor, an opening and a baffle. The processing chamber has a wafer base on which a substrate is mounted. A top plasma source chamber is installed in the processing chamber. The reactor is installed in the top plasma source chamber; has a channel through which a gas flows; and supplies plasma reaction products to the processing chamber. The inductor is installed between the top plasma source chamber and the reactor and wraps around the reactor. An aperture is provided between the reactor perimeter, in which the inductor is housed, and the process chamber. The shutter opens and closes the aperture. Thus, the uniform radial distribution of the various radicals emanating from a plasma source can be improved.

Description

Inductively Coupled Plasma Device

technical field

The invention relates to an inductively coupled plasma system used in chemical vapor deposition (CVD).

Background technique

The plasma treatment of semiconductor workpieces has the advantage of low treatment temperatures and high efficiency. For example, the deposition of SiO ₂ can be performed at a temperature below 200° C. using an O ₂ plasma source and SiH ₄ gas at a deposition rate of about 100-500 nm/min. However, in order to deposit large areas (up to 300 mm diameter wafers) with high coating uniformity, the plasma source must have a high throughput and form the plasma with a uniform flux. These requirements are met by several high density plasma sources (HDP) available in the art.

Although historically HDPs were developed from electron cyclotron resonance (ECR) plasmas, most recent applications are based on radio frequency (RF) excited inductively coupled plasmas (ICP). The various ICP sources are simple in design, have a wide power and pressure window, and do not require auxiliary magnets for their operation. A flat helical coil inductor has been enhanced for its high deposition and etch efficiency (see eg US Patent No. 6184158). Unfortunately, there are some inherent disadvantages of this type of ICP source. RF power from a coil to a process chamber must be fed through a dielectric window, typically made of quartz. The thickness of this window must be large enough to withstand atmospheric pressure - several cm. For large devices, the thickness of the window must be greater. The vacuum side of the dielectric window is subject to sputtering due to high voltage on the coil and largely capacitive coupling.

A helical resonator is a type of ICP source that operates at the resonance of a helical induction coil (US Patent No. 5965034). Resonance is obtained by tuning the length L of an induction wire to an excitation discharge, associated with a wavelength λ of an RF electromagnetic field. Resonance condition: L=(λ/4)*m, where m is an integer. Different values of m correspond to different standing wave modes in the inductor. Each end of the coil can be grounded or floating, which defines different boundary conditions for the current and voltage waveforms. The RF tap location is usually midway, between the ends of the coil. By changing the boundary conditions and the length of the induction line, this plasma source can balance various parasitic capacitive coupling effects. [G.K. Vinogradov. "Transmission line balanced inductive plasma sources". Plasma Sources Sci. Technol. 9(2000) 400-412]. Such a plasma source has a cylindrical geometry and must have a dielectric head-plasma-container. This is usually a cylindrical quartz tube (reactor) which also forms the side walls of a plasma source vacuum chamber.

The induction coils are balanced to minimize the plasma potential and thus the sputtering of a reactor material relative to a grounded surface. Such induction coils exhibit high effectiveness and radial uniformity for dry etching at 1 Torr or higher. However, at pressures below 10 mTorr, HDP with cylindrical geometry may lose radial uniformity of gas flow due to ion pumping action leading to depletion of neutral species in an axial region. This effect is more significant at low pressure and high plasma density, ie high concentration of charged particles. The most significant variations in neutral uniformity are likely to occur in large-area plasma sources [G.R. Tynan. "Neutraldepletion and transport mechanisms in large-area high density plasma sources" J.Appl.Phys.86(1999)4356 ].

In most applications of ICP sources, an inductor is external to a vacuum chamber. Positioning the sensors outside the chamber has certain disadvantages:

1. It requires some huge, complex dielectric vacuum vessel for a helical inductor, or some large area dielectric orifices in the case of a flat spiral inductor.

2. An external sensor is not compatible with Ultra High Voltage (UHV) designs.

3. The ratio of the conductive portion of the chamber to a wafer susceptor is too small, although it is desirable to have a susceptor surface area much smaller than the ground surface area to achieve control of negative bias on a substrate without applying high RF energy Chance.

4. It is difficult to scale up the system.

The HDP source can be used in a Radical Accelerated Sequential (RAS) CVD process (US Patent No. 6200893). The concept of RAS CVD is similar to atomic layer deposition (ALD), where two precursors are fed to the substrate in a time-segmented manner. This differs from ALD in that one of the precursors is a free radical but not a stable compound. This method guarantees the controlled deposition of monolayers with perfect thickness uniformity. However, this treatment is not very effective if one of the precursors, ie the stable compound, has a low probability of adhesion.

Contents of the invention

In order to solve the above-mentioned various problems, an object of the present invention is to provide a high-density plasma device capable of eliminating sputtering of the inductor and preventing each gas product from flowing back and approaching the inductor.

Another object of the present invention is to provide a high density plasma device that can form a uniform radial distribution of free radicals originating from a plasma source.

Therefore, in order to achieve the above objects, according to the present invention, an inductively coupled plasma device is provided, comprising a processing chamber, a top plasma source chamber, a reactor, an inductor, an opening and a barrier plate. The processing chamber has a wafer base on which a substrate is mounted. The top plasma source chamber is mounted on the processing chamber. The reactor is installed in the top plasma source chamber, has a channel through which a certain gas flows, and supplies plasma reaction products to the processing chamber. The inductor is installed between the top plasma source chamber and the reactor and wraps around the reactor. The opening is provided between the peripheral space of the reactor, in which the inductor is installed, and the process chamber. The shutter opens and closes the aperture.

The reactor includes an inner cylinder, an outer cylinder and an annular channel. The outer cylinder surrounds the inner cylinder. The annular passage is arranged between the inner cylinder and the outer cylinder. Preferably, the top of the annular channel is connected to a gas sump outside the top plasma source chamber.

According to an embodiment of the invention, the bottom of the inner cylinder is narrowed so that the bottom of the annular passage between the inner and outer cylinders becomes a circle. A gas distribution plate, having a plurality of perforations, fits over the annular channel. In more detail, a plurality of gas distribution plates are spaced apart from each other above the annular channel.

The wafer susceptor electrically floats within the processing chamber. Specifically, the wafer susceptor is supported within the processing chamber by a ceramic vacuum interrupter.

Preferably, a purge inert gas is supplied to the space surrounding the inductor in the top plasma source chamber in which the inductor is housed. In addition, preferably, the length of the induction coil is equal to 1/4 wavelength of a high frequency electromagnetic field. Preferably, high frequency power is supplied to one of the turns of the induction coil between two ends of the induction coil, both ends of which are grounded or floating. Preferably, the high and low frequency electromagnetic fields are switched on and off periodically or in some given order.

Preferably, a bipolar pulse of DC voltage is applied to the substrate. Preferably, the pulsing of the electromagnetic field is synchronized with the pulsing of the gas source and the gases are supplied sequentially, thereby achieving an improved free radical accelerated sequential deposition process.

Description of drawings

The above objects and advantages of the present invention will become more apparent by describing in detail its various embodiments with reference to the accompanying drawings, in which:

Fig. 1 is a sectional side view of a preferred embodiment of an inductively coupled plasma (ICP) device of the present invention;

2A is a schematic diagram of a top plasma source chamber in the ICP apparatus shown in FIG. 1;

2B is a cross-sectional view of a top plasma source chamber in the ICP apparatus shown in FIG. 1;

Fig. 3 is a plan view of a gas distribution plate installed at the top of the top plasma source chamber in the ICP apparatus shown in Fig. 1;

Figure 4 is a flow diagram of a radical accelerated sequence (RAS) deposition process consistent with the present invention.

Detailed ways

Figure 1 shows a cross-sectional side view of a preferred embodiment of an inductively coupled plasma (ICP) apparatus of the present invention. The ICP device includes a top plasma source chamber 1 and a processing chamber 2

A plasma source is arranged inside the top plasma source chamber 1 . The plasma source includes a spiral induction coil 4 and a plasma reactor 3 . The plasma reactor 3 is connected by means of a screw cap and a bellows 12 to a gas line 20 for supplying _O2 , _N2 , Ar and the like. The RF energy for exciting the plasma in the plasma reactor 3 is fed to one of the turns of the induction coil 4 via an RF cable 11 and an RF feed through (not shown). Both ends of the induction coil 4 are grounded. The entire length of the induction coil 4 is equal to the full wavelength of an RF electromagnetic field. Under these conditions, standing waves of voltage and current are formed in the induction coil 4 . Preferably, the induction coil 4 should have a resonant length, since for large systems it is difficult to make the inductor wire short enough to eliminate current and voltage deviations along the induction coil 4 . Therefore, it is better to tune it to resonance.

The purpose of the plasma source is to generate a flux of radicals when a gas or gas mixture selected from O ₂ , N ₂ , C ₂ F ₆ , Ar, He etc. passes through the plasma reactor 3 .

The bottom end of the plasma reactor 3 is open so that the plasma products are in fluid communication with the processing chamber 2 . Another reagent, according to a remote plasma principle, is supplied directly to the processing chamber 2 without undergoing decomposition in plasma. This reactant, such as SiH ₄ , mixed with an inert gas, is fed through a gas injection ring 5 having a plurality of holes. The gas injection ring 5 creates an azimuthal uniform distribution of the gas flow and prevents backflow of the various reaction products into the gas line 20 .

A substrate is placed on a wafer susceptor comprising a heating plate 6, a bellows 7 and a ceramic vacuum break 8. The heating plate 6 is made movable so that the distance between the substrate and the gas injection ring 5 can be adjusted for better radial uniformity of the coating.

A ceramic vacuum interrupter 8 insulates the wafer susceptor from the processing chamber 2 so that the substrate has a floating potential. The various reaction products are evacuated through a discharge orifice 10 . The plasma reactor 3 has an annular inner channel 33, shown in Fig. 2B. The plasma reactor 3 consists of two dielectric cylinders 31 and 32 with different diameters. One of the inner tubes 31 is closed from the bottom and opened from the top. In contrast, the tub 32 is open from the bottom and closed from the top. As a result, an annular inner channel 33 for exciting and transporting the plasma 14 is formed. The cross-section of the annular inner channel 33 in the bottom part gradually changes from annular to circular. A bottom perimeter 18 of the inner barrel 31 acts as a baffle, altering the flow of charged and neutral particles in the axial portion of the plasma source. The design of this reactor:

1) Minimize the effective plasma volume, thereby increasing the specific power absorption;

2) Minimize the reflux of various reaction products into the plasma;

3) Improved uniformity of neutral species velocities; and

4) Minimize the neutral depletion effect caused by ion pumping, thereby forming the radial uniformity of the neutral species at the outlet of the plasma source.

As shown in FIGS. 1 , 2A and 2B, the space between the periphery of a reactor 3 and the walls of a plasma source chamber 15 is used for arranging the induction coil 4 . At low pressure, discharges can be induced in this space and sputtering of the induction coil 4 can occur. However, in many cases it is desirable to have process pressures as low as 1-10 mTorr. This sputtering problem is solved by using the baffle 9 shown in Figures 1 and 2A. The baffle 9 is disposed between the plasma source chamber 1 and the processing chamber 2 to open (shown in FIG. 1 ) or close (shown in FIG. 2A ) the opening 19 . When the shutter 9 is opened, the entire volume of the plasma source between the plasma source chamber 1 and the plasma reactor 3 is evacuated. When an inert gas flow passes through the gap between the plasma reactor 3 and the wall of the plasma source chamber 1, the closed baffle 9 will cause a pressure high enough to eliminate the sputtering of the induction coil 4, and the plasma The pressure in the reactor 3 is the same as in the process chamber 2 . The baffle 9 also prevents various reaction products from flowing back into the vicinity of the induction coil 4 .

The azimuthal uniformity of the gas flow in the plasma source in the plasma source chamber 1 is formed by means of two gas distribution plates 13 . The gas distribution plates 13 are spaced apart from each other above the annular inner channel 33 of the plasma reactor 3 , the schematic structure of which is shown in FIG. 3 . This figure shows an annular plate 13 with a plurality of holes 17 distributed symmetrically. The gas distribution plates 13 together with the baffles 9 form a pressure distribution which prevents various reaction products from flowing back into the plasma source and gas lines 20 .

Referring to FIG. 2, the pressure relationship is P<P2<P1<P3, where P is the process pressure and P3 is the pressure in the sensing area. Since the wafer susceptor is floating in this embodiment, it can be connected to an auxiliary power source. This auxiliary power supply must provide a low frequency voltage or a bipolar direct current (DC) pulse of a voltage to achieve controlled excitation and ionization of the gas near the wafer. In most cases, this greatly simplifies the deposition process, which is too slow in conventional remote plasma CVD. Radical-accelerated sequential deposition (radical -assisted sequential deposition). To this end, pulses of high power electrical power are synchronized with pulses of one reagent source, such as _O2 , and pulses of low power power are synchronized with pulses of another reagent, such as _SiH4 .

A schematic diagram of this modified radical accelerated deposition process is shown in FIG. 4 . It differs from existing methods in the prior art in that the molecular precursor is excited by a voltage pulse applied to the wafer susceptor.

As mentioned above, the actual plasma volume is minimized and thus the specific energy absorption is increased. In addition, backflow of various reaction products into the plasma is minimized and uniformity of velocity of neutral species is improved. Second, neutral depletion effects due to ion pumping are minimized, thereby creating a radial uniformity of neutral species at the exit of the plasma source.

Although the invention has been described with reference to a specific embodiment, it will be apparent to those skilled in the art that various modifications of the described embodiments can be made without departing from the scope of the invention defined by the appended claims. The spirit and scope of the invention are claimed to be determined. The disclosure and publication of the matters described in the present invention are exemplary only and are not to be construed as limiting the scope of the present invention as defined by the appended claims.

Claims (13)

1. inductive coupling type plasma device comprises:

One treatment chamber has the wafer base of an installing on it one substrate;

One top plasma source chamber is installed on the treatment chamber;

One is installed in the reactor among the plasma source chamber of top, has a gas by it passage that flows through, and the plasma reaction product is supplied with treatment chamber;

One induction coil is installed between top plasma source chamber and the reactor and is wound in reactor;

One perforate is arranged between the reactor peripheral space and treatment chamber of wherein installing induction coil

And

The baffle plate of the described perforate of one opening and closing.

2. according to the described inductive coupling type plasma device of claim 1, wherein reactor comprises:

One inner cylinder;

One outer cylinder around inner cylinder; And

One circular passage is arranged between inner core and the urceolus,

Wherein the top of circular passage is connected in a gas line of plasma source chamber outside, top.

3. according to the described inductive coupling type plasma device of claim 2, wherein the bottom surface of inner cylinder narrows down, and making the bottom of the circular passage between inner cylinder and the outer cylinder become is a circle

4. according to claim 2 or 3 described inductive coupling type plasma devices, wherein above the circular passage, be equiped with gas distribution plate with many eyelets.

5. according to the described inductive coupling type plasma device of claim 4, wherein above the circular passage, be provided with the gas distribution plate that a plurality of each intervals come.

6. according to claim 1 or 2 described inductive coupling type plasma devices, wherein wafer base is floated among treatment chamber with electric means.

7. according to the described inductive coupling type plasma device of claim 6, wherein wafer base is supported by a ceramic vacuum circuit breaker in treatment chamber.

8. according to the described inductive coupling type plasma device of claim 1, wherein an inert gas that purges usefulness infeeded in the plasma source chamber of top, induction coil is installed in reactor peripheral space wherein.

9. according to the described inductive coupling type plasma device of claim 1, wherein high-frequency energy is supplied with one of each circle of induction coil between the induction coil two ends, and the two ends of induction coil be ground connection or float.

10. according to the described inductive coupling type plasma device of claim 1, wherein high and low frequency electromagnetic field periodically or according to one givenly connects in turn and disconnects.

11. according to the described inductive coupling type plasma device of claim 1, wherein each bipolar pulse of a dc voltage puts on substrate.

12. according to the described inductive coupling type plasma device of claim 10, wherein the impulsive synchronization of the pulse of electromagnetic field and source of the gas and gas is by sequentially feeding, thereby implements a kind of improved free radical accelerating type sequential aggradation process.

13. according to the described inductive coupling type plasma device of claim 11, wherein the impulsive synchronization of the pulse of electromagnetic field and source of the gas and gas is by sequentially feeding, thereby implements a kind of improved free radical accelerating type sequential aggradation process.

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